Method of determining water content of ethanol for ffv and correcting fuel quantity based on water content

Abstract

A method of determining the water content of ethanol for an FFV and correcting fuel quantity based on the water content, which verifies whether an oxygen sensor is normal or abnormal, and it is determined whether ethanol learning conditions have been satisfied. It is determined whether learned concentration of ethanol is 100%. If the oxygen sensor is normal, the ethanol learning conditions are satisfied, and the ethanol concentration is 100%, it is determined that water is contained in the ethanol if a quantity of fuel learned by the oxygen sensor is greater than a predetermined reference value. If it is determined that water is contained in the ethanol, water content corresponding to the learned quantity of fuel is calculated from a map of water contents correlated with learned fuel quantities.

What is claimed is: 
     
         1 . A method of determining water content of ethanol for a Flexible Fuel Vehicle (FFV), comprising:
 a) verifying whether an oxygen sensor is normal or abnormal, and determining whether ethanol learning conditions have been satisfied;   b) determining whether learned concentration of ethanol is 100%;   c) if the oxygen sensor is normal, the ethanol learning conditions are satisfied, and the ethanol concentration is 100%, determining that water is contained in the ethanol when a quantity of fuel learned by the oxygen sensor is greater than a predetermined reference value; and   d) if it is determined in c) that water is contained in the ethanol, calculating water content corresponding to the learned quantity of fuel from a map of water contents correlated with learned fuel quantities.   
     
     
         2 . The method according to  claim 1 , wherein in a), the ethanol learning conditions are determined to have been satisfied when temperature of a coolant of the engine falls within a predetermined temperature range indicative of a normal operating state of the engine and a number of rotations of the engine is maintained in a steady state other than a state of either rapid acceleration or rapid deceleration. 
     
     
         3 . The method according to  claim 1 , further comprising:
 if it is determined in b) that the learned ethanol concentration is not 100%, and if it is determined in c) that the quantity of fuel learned by the oxygen sensor is equal to or less than the predetermined reference value, performing normal learning of the quantity of fuel.   
     
     
         4 . A method of determining water content of ethanol for a Flexible Fuel Vehicle (FFV) and correcting fuel quantity based on the water content, comprising:
 a) verifying whether an oxygen sensor is normal or abnormal, and determining whether ethanol learning conditions have been satisfied;   b) determining whether learned concentration of ethanol is 100%;   c) if the oxygen sensor is normal, the ethanol learning conditions are satisfied, and the ethanol concentration is 100%, determining that water is contained in the ethanol when a quantity of fuel learned by the oxygen sensor is greater than a predetermined reference value;   d) if it is determined in c) that water is contained in the ethanol, calculating water content corresponding to the learned quantity of fuel from a map of water contents correlated with learned fuel quantities; and   e) comparing the water content calculated in d) with a map of basic fuel quantities correlated with water contents, obtaining a basic quantity of fuel corresponding to the water content calculated in d), and injecting the fuel based on the basic quantity of fuel.   
     
     
         5 . The method according to  claim 4 , wherein:
 if it is verified in a) that the oxygen sensor is abnormal, a warning prompting inspection of a vehicle is provided and control is terminated, and   in a), the ethanol learning conditions are determined to have been satisfied when temperature of a coolant of the engine falls within a predetermined temperature range indicative of a normal operating state of the engine and a number of rotations of the engine is maintained in a steady state other than a state of either rapid acceleration or rapid deceleration.   
     
     
         6 . The method according to  claim 4 , further comprising:
 if it is determined in b) that the learned ethanol concentration is not 100%, and if it is determined in c) that the quantity of fuel learned by the oxygen sensor is equal to or less than the predetermined reference value, performing learning of the quantity of fuel using an output value of the oxygen sensor.   
     
     
         7 . The method according to  claim 4 , wherein the predetermined reference value with which the quantity of fuel learned by the oxygen sensor is to be compared in c) is set to a value ranging from about 3% to about 9%. 
     
     
         8 . The method according to  claim 4 , wherein, after e), c) is repeatedly performed to continuously determine and calculate the water content of the ethanol, and then the basic quantity of fuel is corrected based on the water content.